Document and Entity Information Document - USD ($)	12 Months Ended
Document and Entity Information Document - USD ($)	Dec. 31, 2017	Mar. 01, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	OptiNose, Inc.
Entity Central Index Key	0001494650
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		37,865,740
Entity Public Float			$ 0
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 234,854	$ 36,797
Grants and other receivables	46	384
Inventory	2,013	0
Deposits and other current assets	1,254	3,494
Total current assets	238,167	40,675
Property and equipment, net	2,564	323
Deposits and other assets — long-term	405	553
Total assets	241,136	41,551
Current liabilities:
Accounts payable	5,893	3,369
Accrued expenses	8,698	2,541
Deferred other income	186	0
Total current liabilities	14,777	5,910
Convertible notes payable, net	0	15,256
Long-term debt, net	71,863	0
Accrued interest	0	3,409
Total liabilities	86,640	24,575
Commitments and contingencies (Note 11)
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	0	168,173
Stockholders' equity (deficit):
Common stock, $0.001 par value; 200,000,000 and 10,624,486 shares authorized at December 31, 2017 and December 31, 2016 , respectively; 37,802,556 and 4,067,717 shares issued and outstanding at December 31, 2017 and December 31, 2016, respectively	38	4
Additional paid-in capital	365,838	0
Accumulated deficit	(211,269)	(151,102)
Accumulated other comprehensive loss	(111)	(99)
Total stockholders' equity (deficit)	154,496	(151,197)
Total liabilities, redeemable convertible preferred stock and stockholders' equity (deficit)	241,136	41,551
Redeemable Convertible Preferred Stock, Series A
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	0	5,381
Redeemable Convertible Preferred Stock, Series B1
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	0	673
Redeemable Convertible Preferred Stock, Series B2
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	0	14,760
Redeemable Convertible Preferred Stock, Series C
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	0	105,738
Redeemable Convertible Preferred Stock, Series C1
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	$ 0	$ 41,621

Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Redeemable convertible preferred stock, par value (usd per share)	$ 0	$ 0.001
Shares authorized (in shares)	8,932,851	6,875,514
Common stock, par value (usd per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	200,000,000	10,624,486
Shares issued (in shares)	37,802,556	4,067,717
Shares outstanding (in shares)	37,802,556	4,067,717
Redeemable Convertible Preferred Stock, Series A
Shares authorized (in shares)	0	285,480
Shares issued (in shares)	0	285,480
Shares outstanding (in shares)	0	285,480
Redeemable Convertible Preferred Stock, Series B1
Shares authorized (in shares)	0	35,680
Shares issued (in shares)	0	35,680
Shares outstanding (in shares)	0	35,680
Redeemable Convertible Preferred Stock, Series B2
Shares authorized (in shares)	0	782,600
Shares issued (in shares)	0	782,600
Shares outstanding (in shares)	0	782,600
Redeemable Convertible Preferred Stock, Series C
Shares authorized (in shares)	0	4,115,344
Shares issued (in shares)	0	4,115,344
Shares outstanding (in shares)	0	4,115,344
Redeemable Convertible Preferred Stock, Series C1
Shares authorized (in shares)	0	1,656,410
Shares issued (in shares)	0	1,656,410
Shares outstanding (in shares)	0	1,656,410

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Licensing revenues	$ 0	$ 47,500	$ 85
Operating expenses:
Research and development	16,832	15,311	22,156
Selling, general and administrative	31,698	6,869	6,006
Total operating expenses	48,530	22,180	28,162
(Loss) income from operations	(48,530)	25,320	(28,077)
Other (income) expense:
Grant and other income	(162)	(727)	(643)
Interest income	(303)	(143)	(28)
Interest expense	910	3,517	819
Foreign currency (gains) losses	(73)	60	89
Net (loss) income	(48,902)	22,613	(28,314)
Deemed dividend	11,969	11,005	9,992
Accretion to redemption value	1,096	2,109	2,069
Net (loss) income attributable to common stockholders	$ (61,967)	$ 9,499	$ (40,375)
Net (loss) income per share of common stock,
basic (in USD per share)	$ (5.63)	$ 0.40	$ (9.97)
diluted (in USD per share)	$ (5.63)	$ 0.32	$ (9.97)
Weighted average common shares outstanding,
basic (in shares)	10,999,121	4,054,316	4,049,668
diluted (in shares)	10,999,121	4,980,181	4,049,668

Consolidated Statements of Comprehensive Income and Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (48,902)	$ 22,613	$ (28,314)
Other comprehensive (loss) income:
Foreign currency translation adjustment	(12)	42	(13)
Comprehensive (loss) income	$ (48,914)	$ 22,655	$ (28,327)

Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Deficit - USD ($) $ in Thousands	Total	Common Stock	Additional Paid -in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Redeemable Convertible Preferred Stock	Redeemable Convertible Preferred Stock, Series C1	Redeemable Convertible Preferred Stock, Series C and C-1	Redeemable Convertible Preferred Stock, Series C and C-1 Additional Paid -in Capital	Redeemable Convertible Preferred Stock, Series C and C-1 Accumulated Deficit	Redeemable Convertible Preferred Stock, Series C and C-1, In Lieu of Dividend	Redeemable Convertible Preferred Stock, Series C and C-1, In Lieu of Dividend Additional Paid -in Capital	Redeemable Convertible Preferred Stock, Series C and C-1, In Lieu of Dividend Accumulated Deficit	Redeemable Convertible Preferred Stock, Series C2	Redeemable Convertible Preferred Stock, Series D	Redeemable Convertible Preferred Stock, Series C, C1, D	Redeemable Convertible Preferred Stock, Series C, C1, D Additional Paid -in Capital	Redeemable Convertible Preferred Stock, Series C, C1, C2, and D	Redeemable Convertible Preferred Stock, Series C, C1, C2, and D Additional Paid -in Capital	Redeemable Convertible Preferred Stock, Series C, C1, C2, and D Accumulated Deficit
Shares outstanding (in shares) at Dec. 31, 2014						6,638,885
Beginning balance at Dec. 31, 2014						$ 138,160
Shares outstanding (in shares) at Dec. 31, 2014		4,049,668
Beginning balance at Dec. 31, 2014	$ (121,592)	$ 4	$ 0	$ (121,468)	$ (128)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of Series D preferred stock, net of issuance costs (in shares)							236,629
Sale of Series D preferred stock, net of issuance costs							$ 4,838
Stock compensation expense	588		588
Accretion of preferred stock								$ 2,069			$ 9,992					$ 2,069		$ 9,992
Accretion of preferred stock								(2,069)	$ (588)	$ (1,481)	(9,992)	$ 0	$ (9,992)
Foreign currency translation adjustment	(13)				(13)
Net loss	(28,314)			(28,314)
Shares outstanding (in shares) at Dec. 31, 2015						6,875,514
Ending balance at Dec. 31, 2015						$ 155,059
Shares outstanding (in shares) at Dec. 31, 2015		4,049,668
Ending balance at Dec. 31, 2015	(161,392)	$ 4	0	(161,255)	(141)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation expense	$ 599		599
Exercise of common stock options (in shares)	18,049
Exercise of common stock options	$ 55
Accretion of preferred stock								2,109			11,005					2,109		11,005
Accretion of preferred stock								$ (2,109)	$ (654)	$ (1,455)	$ (11,005)	$ 0	$ (11,005)
Foreign currency translation adjustment	42				42
Net loss	22,613			22,613
Shares outstanding (in shares) at Dec. 31, 2016						6,875,514	1,656,410
Ending balance at Dec. 31, 2016						$ 168,173
Shares outstanding (in shares) at Dec. 31, 2016		4,067,717.000
Ending balance at Dec. 31, 2016	(151,197)	$ 4	0	(151,102)	(99)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of convertible securities (in shares)		25,068,556				8,680,566								687,474
Conversion of convertible securities	237,259	$ 25	237,234			$ (237,259)								$ 19,527
Sale of Series D preferred stock, net of issuance costs (in shares)															1,117,578
Sale of Series D preferred stock, net of issuance costs															$ 36,494
Stock compensation expense	$ 5,096		5,096
Exercise of common stock options (in shares)	41,283
Exercise of common stock options	$ (154)
Accretion of preferred stock																1,096		11,969
Accretion of preferred stock																$ (1,096)	$ (1,096)	$ (11,969)	$ (704)	$ (11,265)
Sale of common stock upon consummation of initial public offering, net of issuance costs (in shares)		8,625,000
Sale of common stock upon consummation of initial public offering, net of issuance costs	125,471	$ 9	125,462
Foreign currency translation adjustment	(12)				(12)
Net loss	(48,902)			(48,902)
Shares outstanding (in shares) at Dec. 31, 2017						0	0
Ending balance at Dec. 31, 2017						$ 0
Shares outstanding (in shares) at Dec. 31, 2017		37,802,556
Ending balance at Dec. 31, 2017	$ 154,496	$ 38	$ 365,838	$ (211,269)	$ (111)

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net (loss) income	$ (48,902)	$ 22,613	$ (28,314)
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	164	83	75
Stock-based compensation	5,096	599	588
Amortization of debt discount and issuance costs	198	776	195
Loss on sale of equipment	2	0	0
Changes in operating assets and liabilities:
Grants and other receivables	337	65	144
Deposits and other assets	2,387	(3,888)	1,504
Inventory	(2,013)	0	0
Accounts payable	392	(130)	450
Accrued expenses	5,834	(1,097)	(3,814)
Accrued interest	668	2,740	669
Deferred other income	186	(41)	(211)
Cash (used in) provided by operating activities	(35,651)	21,720	(28,714)
Investing activities:
Purchases of property and equipment	(2,406)	(215)	(80)
Cash used in investing activities	(2,406)	(215)	(80)
Financing activities:
Proceeds from the sale of common stock units in connection with initial public offering	138,000	0	0
Proceeds from issuance of convertible notes payable, net	0	0	14,285
Proceeds from long-term debt	75,000	0	0
Proceeds from the exercise of stock options	134	55	0
Payments of withholdings on shares withheld for income taxes	(288)	0	0
Cash paid for financing costs	(13,433)	0	(162)
Cash provided by financing activities	236,125	55	19,123
Effects of exchange rate changes on cash and cash equivalents	(11)	39	(14)
Net increase in cash and cash equivalents	198,057	21,599	(9,685)
Cash and cash equivalents at beginning of period	36,797	15,198	24,883
Cash and cash equivalents at end of period	234,854	36,797	15,198
Supplemental disclosure of noncash financing activities:
Financing costs within accounts payable and accrued expenses	2,454	0	0
Conversion of convertible notes payable and accrued interest into Series C-2 preferred stock	237,259	0	0
Redeemable Convertible Preferred Stock, Series C1
Financing activities:
Proceeds from the sale of preferred stock	0	0	5,000
Redeemable Convertible Preferred Stock, Series D
Financing activities:
Proceeds from the sale of preferred stock	36,712	0	0
Redeemable Convertible Preferred Stock, Series C, C1, C2, and D
Supplemental disclosure of noncash financing activities:
Deemed dividend	11,969	11,005	9,992
Redeemable Convertible Preferred Stock, Series C, C1, D
Supplemental disclosure of noncash financing activities:
Deemed dividend	1,096	2,109	2,069
Redeemable Convertible Preferred Stock, Series C2
Supplemental disclosure of noncash financing activities:
Conversion of convertible notes payable and accrued interest into Series C-2 preferred stock	$ 19,527	$ 0	$ 0

Organization and Description of Business	12 Months Ended
Organization and Description of Business	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business OptiNose, Inc. (the Company) was incorporated in Delaware in May 2010 (inception) and has facilities in Yardley, Pennsylvania, Ewing, New Jersey, Oslo, Norway and Swindon, England. The Company's predecessor entity, OptiNose AS, was formed under the laws of Norway in September 2000. In 2010, OptiNose AS became a wholly-owned subsidiary of the Company as part of an internal reorganization. The Company is a specialty pharmaceutical company focused on the development and commercialization of products for patients treated by ear, nose and throat (ENT) and allergy specialists. The Company's first two products approved by the United States Food and Drug Administration (FDA) utilize its proprietary Exhalation Delivery Systems (EDS), which are capable of deep intranasal deposition of medication. OptiNose developed its first product, Onzetra^® Xsail^® (sumatriptan nasal power) through the completion of Phase III clinical trials and subsequently out-licensed the product to Avanir Pharmaceuticals, Inc (Avanir). Onzetra Xsail received FDA approval and was launched in the United States (US) in 2016. The Company's second product, XHANCE^TM (fluticasone propionate) nasal spray, 93 mcg, is a therapeutic that utilizes its EDS to deliver a topically-acting corticosteroid for the treatment of chronic rhinosinusitis with nasal polyps and, if approved, chronic rhinosinusitis without nasal polyps. On September 18, 2017, the FDA approved the Company's New Drug Application (NDA) for XHANCE for the treatment of nasal polyps in patients 18 years of age or older, and XHANCE is in development for the treatment of chronic sinusitis. In October 2017, the Company completed an initial public offering (IPO) of its common stock, selling 8,625,000 shares at $16.00 per share. As a result of the IPO, the Company received $125,471 in net proceeds, after deducting discounts and commissions of $9,660 and offering expenses of approximately $2,869 payable by the Company. Upon consummation of the IPO, all of the outstanding shares of the Company’s redeemable convertible preferred stock were converted into an aggregate of 25,068,556 shares of common stock.

Liquidity	12 Months Ended
Liquidity	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Liquidity	Liquidity Since inception, the Company's operations have focused on organization and staffing, business planning, raising capital, establishing an intellectual property portfolio, conducting preclinical studies and clinical trials, pursuing regulatory approvals and most recently, preparing for the launch of XHANCE. The Company has not generated any revenue from product sales to date. As of December 31, 2017, the Company had cash and cash equivalents of $234,854. During the year ended December 31, 2017, the Company sold 1,117,578 shares of Series D preferred stock, which resulted in gross proceeds to the Company of $36,712 (Note 12). Additionally, in October 2017, the Company completed an IPO of its common stock, selling 8,625,000 shares at $16.00 per share. As a result of the IPO, the Company received $125,471 in net proceeds. In December 2017, the Company entered into a note purchase agreement which provided for the issuance of up to $100,000 of senior secured notes, of which $75,000 (Note 9) of such notes were issued immediately. The Company may need to secure additional capital in the future through equity or debt financings, partnerships, collaborations, or other sources in order to service the Company's existing obligations under outstanding notes, including repayment, and to carry out all of the Company's planned development and commercial activities. If additional capital is not secured when required, the Company may need to delay or curtail its operations until such funding is received. The Company is subject to a number of risks similar to other life sciences companies, including, but not limited to, successful discovery and development of its product candidates, raising additional capital, the development by its competitors of new technological innovations, protection of proprietary technology and market acceptance of the Company's products.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of Significant Accounting Policies

Basis of presentation

The accompanying consolidated financial statements have been prepared in conformity with US generally accepted accounting principles (GAAP). Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification (ASC) and Accounting Standards Updates (ASU) of the Financial Accounting Standards Board (FASB).

Principles of consolidation

The consolidated financial statements include the accounts of OptiNose, Inc. and its wholly-owned subsidiaries, OptiNose US, Inc., OptiNose AS and OptiNose UK Ltd. All inter-company balances and transactions have been eliminated in consolidation.

Use of estimates

The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and reported amounts of expenses during the reporting period. Due to the uncertainty of factors surrounding the estimates or judgments used in the preparation of the consolidated financial statements, actual results may materially vary from these estimates. Estimates and assumptions are periodically reviewed and the effects of revisions are reflected in the consolidated financial statements in the period they are determined to be necessary.

Stock Split

On October 10, 2017, the Company effected a 2.8879-for-1 reclassification, or stock split, of the Company's common stock in connection with its initial public offering, or the IPO. All common share and per share amounts in these consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to reflect the stock split.

Cash and cash equivalents

All highly liquid investments purchased with an original maturity date of three months or less at the date of purchase are considered to be cash equivalents. The Company generally invests its cash in deposits with high credit quality financial institutions. Additionally, the Company performs periodic evaluations of the relative credit standing of these financial institutions.

The Company maintains its cash and cash equivalent balances at foreign and domestic financial institutions. Bank deposits with Norwegian banks are insured up to approximately 2,000 Norwegian krone by the Norwegian Banks' Guarantee Fund. Bank deposits with US banks are insured up to $250 by the Federal Deposits Insurance Corporation. The Company had uninsured cash balances of $233,772 and $35,866 at December 31, 2017 and 2016, respectively.

Fair value of financial instruments

The Company measures certain assets and liabilities at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability (the exit price) in an orderly transaction between market participants at the measurement date. The FASB accounting guidance outlines a valuation framework and creates a fair value hierarchy in order to increase the consistency and comparability of fair value measurements and the related disclosures. In determining fair value, the Company uses quoted prices and observable inputs. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from independent sources. The fair value hierarchy is broken down into three levels based on the source of the inputs as follows:


•	Level 1 — Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities.


•	Level 2 — Valuations based on observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.


•	Level 3 — Valuations based on inputs that are unobservable and models that are significant to the overall fair value measurement.

At December 31, 2017 and 2016, the Company's financial instruments included cash and cash equivalents, grants receivable, accounts payable, and accrued expenses. The carrying amounts reported in the Company's financial statements for these instruments approximates their respective fair values because of the short-term nature of these instruments. In addition, at December 31, 2017, the Company believes the carrying value of debt approximates fair value as the interest rates are reflective of the rate the Company could obtain on debt with similar terms and conditions. At December 31, 2017 and 2016, there were no financial assets or liabilities measured at fair value on a recurring basis.

The Company's financial instruments also included convertible debt at December 31, 2016 (Note 8).

Inventory

Prior to receiving FDA approval for XHANCE in September 2017, inventory purchases were expensed as incurred and recorded as a component of research and development expense. Subsequent to receiving FDA approval, inventories are stated at the lower of cost or net realizable value, net of reserves for excess and obsolete inventory. Cost is computed using standard cost (which approximates actual cost) on a first-in, first-out basis. Inventory consisted of the following:



	December 31,
	2017		2016
Raw materials	$	1,385	$	—
Work-in-process	628		—
Finished goods	—		—
Total	$	2,013	$	—

Deposits and other assets

Deposits and other assets consist primarily of prepaid insurance, payments made in advance to outsourced contract manufacturers and equipment suppliers, as well as a receivable due from the FDA at December 31, 2016 related to a Prescription Drug User Fee Act (PDUFA) New Drug Application fee that the FDA refunded to the Company in March 2017.

Throughout 2017 and 2016, the Company made upfront payments to outsourced plastic mold development manufacturers and equipment suppliers for molds and equipment that are expected to be used for the commercial production of XHANCE. The Company received the majority of this equipment in 2017. For equipment received prior to FDA approval, the Company recorded the cost associated with the equipment purchase as a component of research and development expense if there was no alternative future use of the equipment without FDA approval. Conversely, deposits on equipment received after the September 18, 2017 FDA approval of XHANCE were capitalized as fixed assets when the equipment was received and therefore classified as long-term deposits at December 31, 2017.

Property and equipment

Property and equipment is recorded at cost less accumulated depreciation. Significant additions or improvements are capitalized, and expenditures for repairs and maintenance are charged to expense as incurred. Gains and losses on disposal of assets are included in the consolidated statements of operations. Depreciation is calculated on a straight-line basis over the estimated useful lives of the respective assets.

The estimated useful lives of equipment are as follows:



Computer equipment	3 years
Software	3 years
Machinery & production equipment	5-10 years
Furniture & fixtures	3-5 years
Leasehold improvements	Shorter of lease term or useful life

Long lived assets

Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future net cash flows expected to be generated. Impairment charges are recognized at the amount by which the carrying amount of an asset exceeds the fair value of the asset. Assets to be disposed of are reported at the lower of the carrying amount or the fair value less costs to sell. The Company has not recognized any impairment or disposition of long-lived assets for the years ended December 31, 2017 , 2016 or 2015.

Revenue recognition

Through December 31, 2017, the Company's revenues have been generated through licensing arrangements, which generally contain multiple elements, or deliverables, including licenses and research and development activities to be performed by the Company on behalf of the licensee. Revenues are recognized when (1) persuasive evidence of an arrangement exists, (2) delivery has occurred or services have been rendered, (3) the price is fixed or determinable and (4) collectibility is reasonably assured.

To date, the Company's revenues have been generated pursuant to the terms of a single license agreement (the AVP-825 License Agreement) with Avanir Pharmaceuticals, Inc. (Avanir) (Note 7). The AVP-825 License Agreement includes licensed rights to patented technology, non-refundable up-front license fees, research services, and regulatory and sales milestones as well as royalty payments. As of December 31, 2017, only possible sales milestones and royalty payments remain to be earned under the license AVP-825 License Agreements. Such amounts would only be earned after net sales in the US, Canada and Mexico exceed a certain threshold.

For arrangements with multiple elements, the Company recognizes revenue in accordance with the FASB ASU No. 2009-13, Multiple-Deliverable Revenue Arrangements, which provides guidance for separating and allocating consideration in a multiple element arrangement. The selling prices of deliverables under an arrangement may be derived using third-party evidence (TPE), or a best estimate of selling price (BESP), if vendor-specific objective evidence of selling price (VSOE) is not available. The objective of BESP is to determine the price at which the Company would transact a sale if the element within the License Agreement was sold on a standalone basis. Deliverables under the arrangement are separate units of accounting if (i) the delivered item has value to the customer on a standalone basis and (ii) if the arrangement includes a general right of return relative to the delivered item, and delivery or performance of the undelivered item is considered probable and substantially within the Company's control. The arrangement consideration that is fixed or determinable at the inception of the arrangement is allocated to the separate units of accounting based on their relative selling prices. The appropriate revenue recognition model is applied to each element and revenue is accordingly recognized as each element is delivered. Management exercises significant judgment in determining whether a deliverable is a separate unit of accounting.

In determining the separate units of accounting for the Company's collaborations, the Company evaluated whether the AVP-825 License Agreement has standalone value to the collaborator based on consideration of the relevant facts and circumstances for each arrangement. Factors considered in this determination include the research and development capabilities of the collaborator and the availability of relevant research expertise in the marketplace. In addition, the Company considers whether or not (i) the collaborator could use the license for its intended purpose without the receipt of the remaining deliverables, (ii) the value of the license was dependent on the undelivered items and (iii) the collaborator or other vendors could provide the undelivered items.

Whenever the Company determines that an element is delivered over a period of time, revenue is recognized using either a proportional performance model, if a pattern of performance can be determined, or a straight-line model over the period of performance, which is typically the research and development term.

Development milestones may be triggered either by the results of the Company's research efforts or by events external to it, such as regulatory approval to market a product. Consideration that is contingent upon achievement of a development milestone is recognized in its entirety as revenue in the period in which the milestone is achieved, but only if the consideration earned from the achievement of a milestone meets all the criteria for the milestone to be considered substantive at the inception of the arrangement. For a milestone to be considered substantive, the consideration earned by achieving the milestone must (i) be commensurate with either the Company's performance to achieve the milestone or the enhancement of the value of the item delivered as a result of a specific outcome resulting from the Company's performance to achieve the milestone, (ii) relate solely to past performance and (iii) be reasonable relative to all deliverables and payment terms in the AVP-825 License Agreement. As of December 31, 2017, all development milestones have been achieved.

Advertising expenses

The Company expenses the costs of advertising, including promotional expenses, as incurred. Advertising expenses were $1,833, $26 and $44 for the years ended December 31, 2017, 2016 and 2015, respectively.

Research and development

Research and development costs are expensed as incurred. Research and development costs consist primarily of device development, clinical trial related costs, and regulatory related costs. The Company enters into agreements with contract research organizations (CROs) to facilitate, coordinate and perform agreed upon research and development activities for the Company's clinical trials. These CRO contracts typically call for the payment of fees for services at the initiation of the contract and/or upon the achievement of certain clinical trial milestones. The Company prepays certain CRO fees whereby the prepayments are recorded as a current or non-current prepaid asset and are amortized into research and development expense over the period of time the contracted research and development services were performed. The Company's CRO contracts generally also included other fees such as project management and pass through fees whereby the Company expenses these costs as incurred, using the Company's best estimate. Pass through fees include, but are not limited to, regulatory expenses, investigator fees, travel costs, and other miscellaneous costs. Pass through fees incurred are based on the amount of work completed for the clinical trials and are monitored through reporting provided by the Company's CROs.

Stock-based compensation

The Company measures and recognizes compensation expense for all stock options awarded to employees and nonemployees and shares issued under the employee stock purchase plan based on the estimated fair value of the awards on the respective grant dates. The Company uses the Black-Scholes option pricing model to value its stock option awards and shares issued under the employee stock purchase plan. The Company recognizes compensation expense for time-based awards on a straight-line basis over the requisite service period, which is generally the vesting period of the award. The Company recognizes compensation expense for performance based awards when the performance condition is probable of achievement. Stock-based awards issued to nonemployees are revalued at each reporting period until the award vests. The Company accounts for forfeitures of stock option awards as they occur.

Estimating the fair value of options and shares issued under the employee stock purchase plan requires the input of subjective assumptions, including the estimated fair value of the Company's common stock, the expected life of the options, stock price volatility, the risk-free interest rate and expected dividends. The assumptions used in the Company's Black-Scholes option-pricing model represent management's best estimates and involve a number of variables, uncertainties and assumptions and the application of management's judgment, as they are inherently subjective.

Income taxes

Income taxes are accounted for under the asset and liability method. The Company recognizes deferred tax assets and liabilities for temporary differences between the financial reporting basis and the tax basis of the Company's assets and liabilities and the expected benefits of net operating loss carryforwards. The impact of changes in tax rates and laws on deferred taxes, if any, applied during the period in which temporary differences are expected to be settled, is reflected in the Company's financial statements in the period of enactment. The measurement of deferred tax assets is reduced, if necessary, if, based on weight of the evidence, it is more likely than not that some, or all, of the deferred tax assets will not be realized. As of December 31, 2017 and 2016, the Company has concluded that a full valuation allowance is necessary for all of its net deferred tax assets. The Company had no amounts recorded for uncertain tax positions, interest or penalties in the accompanying consolidated financial statements.

Grant income

Government grants are agreements that provide cost reimbursement for certain research and development activities over a contractually defined period. Income from government grants is recognized in the period in which related costs are incurred, provided that the conditions under which government grants were provided have been met and only perfunctory obligations are outstanding. Grant income received in excess of costs incurred is recognized as deferred other income.

Net income (loss) per common share

The Company used the two-class method to compute net income (loss) per common share for the year ended December 31, 2016 as the Company realized net income and had issued securities (redeemable convertible preferred stock) that entitled the holder to participate in dividends and earnings of the Company. Under this method, net income is reduced by the amount of any dividends earned and the accretion of redeemable convertible preferred stock to its redemption value during the period. The remaining earnings (undistributed earnings) are allocated to common stock and each series of redeemable convertible preferred stock to the extent that each preferred security may share in earnings as if all of the earnings for the period had been distributed. The total earnings allocated to common stock is then divided by the number of outstanding shares to which the earnings are allocated to determine the earnings per share. The two-class method is not applicable during periods with a net loss, as the holders of the redeemable convertible preferred stock have no obligation to fund losses. For the year ended December 31, 2016, the Company presented diluted net income per common share using the two-class method, which was more dilutive than the "if-converted" method.

Diluted net income (loss) per common share is computed under the two-class method by using the weighted-average number of shares of common stock outstanding, plus, for periods with net income attributable to common stockholders, the potential dilutive effects of stock options, warrants, and convertible debt. In addition, the Company analyzes the potential dilutive effect of the outstanding redeemable convertible preferred stock and convertible debt under the "if-converted" method when calculating diluted earnings per share, in which it is assumed that the outstanding redeemable convertible preferred stock or convertible debt converts into common stock at the beginning of the period or when issued if later. The Company reports the more dilutive of the approaches (two class or "if-converted") as their diluted net income per share during the period.

Basic net income (loss) per common share is determined by dividing net income (loss) applicable to common stockholders by the weighted average common shares outstanding during the period. For the years ended December 31, 2017 and 2015, the outstanding common stock option and common stock warrants have been excluded from the calculation of diluted net income (loss) per share because their effect would be anti-dilutive. Therefore, the weighted average shares used to calculate both basic and diluted net loss per share are the same.

The following table sets forth the computation of basic and diluted net income (loss) per share for the periods indicated:



	Year Ended December 31,
	2017			2016			2015
Basic net (loss) income per common share calculation:
Net (loss) income attributable to common stockholders	$	(61,967	)	$	9,499		$	(40,375	)
Less: undistributed earnings to participating securities	—			(7,884		)	—
Net (loss) income attributable to common stockholders — basic	(61,967		)	1,615			(40,375		)
Weighted average common shares outstanding — basic	10,999,121			4,054,316			4,049,668
Net (loss) income per share of common stock — basic	$	(5.63	)	$	0.40		$	(9.97	)
Diluted net (loss) income per common share calculation:
Net (loss) income attributable to common stockholders	$	(61,967	)	$	9,499		$	(40,375	)
Less: undistributed earnings to participating securities	—			(7,884		)	—
Net (loss) income attributable to common stockholders — diluted	(61,967		)	1,615			(40,375		)
Weighted average common shares outstanding — basic	10,999,121			4,054,316			4,049,668
Stock options	—			925,865			—
Weighted average common shares outstanding — diluted	10,999,121			4,980,181			4,049,668
Net (loss) income per share of common stock — diluted	$	(5.63	)	$	0.32		$	(9.97	)

Diluted net income (loss) per common share for the periods presented do not reflect the following potential common shares, as the effect would be antidilutive:



	Year Ended December 31,
	2017	2016	2015
Stock options	2,141,367	2,346,073	3,413,178
Common stock warrants	1,890,489	1,890,489	1,890,489
Convertible debt	—	1,917,522	1,888,484
Convertible preferred stock	—	19,855,772	19,855,772
Total	4,031,856	26,009,856	27,047,923

Recent accounting pronouncements

In May 2017, the FASB issued ASU No. 2017-09, Stock Compensation - Scope of Modification Accounting. ASU 2017-09 provides guidance on which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The new standard is effective for fiscal years beginning after December 15, 2017. The Company is currently evaluating the potential impact of the adoption of this standard on its results of operations, financial position and cash flows and related disclosures.

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The FASB issued the update to require the recognition of lease assets and liabilities on the balance sheet of lessees. The standard will be effective for fiscal years beginning after December 15, 2018, including interim periods within such fiscal years. The ASU requires a modified retrospective transition method with the option to elect a package of practical expedients. Early adoption is permitted. The Company is currently evaluating the potential impact of the adoption of this standard on its results of operations, financial position and cash flows and related disclosures.

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which will replace numerous requirements in US GAAP, including industry-specific requirements. This guidance provides a five-step model to be applied to all contracts with customers, with an underlying principle that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The new standard also defines accounting for certain costs related to origination and fulfillment of contracts with customers, including whether such costs should be capitalized. This statement requires extensive quantitative and qualitative disclosures covering the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including disclosures on significant judgments made when applying the guidance and assets recognized from costs incurred to obtain or fulfill a contract. The guidance is effective for annual reporting periods beginning after December 15, 2017, and interim periods within that reporting period. An entity can elect to apply the guidance under one of the following two methods: (i) retrospectively to each prior reporting period presented — referred to as the full retrospective method or (ii) retrospectively with the cumulative effect of initially applying the standard recognized at the date of initial application in retained earnings — referred to as the modified retrospective method.

The Company has assessed the impact that ASU No. 2014-09 will have on its financial statements and related disclosures. To date, the Company has derived its revenues from a single licensing agreement with Avanir (the AVP-825 License Agreement). The consideration the Company has received to date includes an upfront payment, research and development funding and development milestone payments. Additionally, the Company is eligible to receive sales milestone payments and royalties in the future once net product sales exceed a certain threshold. The Company analyzed the performance obligations under the AVP-825 License Agreement, and the consideration received to date and that the Company may receive in the future, as part of its analysis of the impact of ASU 2014-09 on this arrangement. The Company has completed its initial assessment of the AVP-825 License Agreement, and currently does not expect the adoption of the ASU to have a material impact on its financial statements but is expected to result in expanded footnote disclosures. The Company will continue to monitor additional changes, modifications, clarifications or interpretations being undertaken by the FASB, which may impact our current conclusion.

The Company plans to adopt the new standard effective January 1, 2018 using the modified retrospective approach.

Property and Equipment

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property and Equipment

Property and equipment, net, consisted of:



	December 31,
	2017			2016
Computer equipment and software	$	307		$	293
Furniture and fixtures	89			121
Machinery and equipment	2,495			255
Leasehold improvements	28			28
	2,919			697
Less: accumulated depreciation	(355		)	(374		)
	$	2,564		$	323

Depreciation expense was $164, $83 and $75 for the years ended December 31, 2017, 2016 and 2015, respectively. During the year ended December 31, 2017, the Company disposed of $209 of fully depreciated assets.

AVP-825 License Agreement	12 Months Ended
AVP-825 License Agreement	Dec. 31, 2017
Research and Development [Abstract]
AVP-825 License Agreement	AVP-825 License Agreement In July 2013, the Company's wholly owned subsidiary, OptiNose AS, entered into the AVP-825 License Agreement with Avanir for the exclusive right to sell AVP-825 (now marketed as Onzetra^® Xsail^®), a product combining a low-dose powder form of sumatriptan with the Company's EDS technology platform, for the acute treatment of migraines in adults and any follow-on products under development that consist of a formulation that contains triptans as the sole active ingredient. Through December 31, 2017, under the terms of the AVP-825 License Agreement, the Company received aggregate cash payments of $70,000 in connection with the initial signing and the achievement of certain development milestones. Under the terms of the License Agreement, the Company is eligible to receive up to $50,000 upon the achievement of sales milestones as well as tiered low double-digit royalty payments on net sales in the US, Canada and Mexico after such cumulative sales exceed a certain threshold. The Company determined that there were two deliverables under the AVP-825 License Agreement: (i) the license which was delivered in July 2013 and (ii) its obligation to provide certain research and development services in execution of the development plan and to share equally in certain qualified third party development costs through FDA approval. The Company concluded that the license had standalone value to Avanir and was separable from the research and development services, given Avanir has significant research capabilities in the field. As a result, the license and research services qualify as separate units of accounting and the value of the license and the value of the research services were separately valued based upon the estimated selling price of each deliverable. The value attributable to the license was recognized up-front upon delivery of the license and the values attributable to the research services were deferred and recognized over the period in which the related services were to be delivered based upon a percentage of costs incurred in each respective reporting period. The estimated selling price of each deliverable was determined using the BESP. The BESP reflects the Company's best estimate of what the selling price would be if the deliverable was regularly sold on a stand-alone basis. In conjunction with the AVP-825 License Agreement, the Company recognized $47,500 as licensing revenue during the year ended December 31, 2016. The revenue was related to the achievement of the FDA approval milestone in January 2016. The Company did not recognize any licensing revenue during the year ended December 31, 2017.

Convertible Notes

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Convertible Notes

At December 31, 2017 and 2016, the Company's convertible notes payable, net, balance was as follows:



	December 31,
	2017		2016
Face amount	$	—	$	15,000
Front end fees	—		(75		)
Debt issuance costs	—		(44		)
Back end fees	—		375
Convertible notes payable, net	$	—	$	15,256

On September 30, 2015, the Company entered into a Senior Secured Convertible Note Purchase Agreement (Notes) with various existing stockholders. The Notes provided the Company with up to $30,000 in capital available in two separate tranches. The first tranche of $15,000 closed on September 30, 2015. The second tranche of up to $15,000 was available to the Company until March 30, 2017 but was never drawn. The Notes bore an annual interest rate of 17% and were scheduled to mature on September 30, 2020 if not otherwise converted to Series C-2 shares. The Notes also bore front-end fees of $450, which were paid at issuance, and back end fees of $450 plus interest that was to be paid at maturity. The Notes could be repaid at any time in $100 increments, did not contain any prepayment penalties and were secured by assets of OptiNose Inc. and OptiNose US, Inc. At the option of the majority purchaser of the Notes after March 30, 2017, or prior to March 30, 2017 if an event of default occurred or was continuing under the Notes, all note principal along with any accrued interest and back end fees thereon, could be converted into Series C-2 shares of preferred stock at a conversion price based upon a Company valuation equal to the lower of fair market value or $300,000.

As of December 31, 2016, the fair value of the Notes was $21,814, which was estimated based on the as converted value of the Notes as of that date.

On March 24, 2017, in connection with the Series D Financing, the Notes and associated accrued interest and back end fees thereon totaling $19,527 converted into 687,474 shares of Series C-2 preferred stock at a per share conversion price of approximately $28.40.

The Company recorded interest expense of $862, $3,517 and $819 during the years ended December 31, 2017, 2016 and 2015, respectively, in conjunction with the Notes. Total coupon interest on the Notes and back end fees was $743 and $2,740 during the years ended December 31, 2017 and 2016, respectively. The front-end fees of $450 were recorded as debt discount at issuance and were amortized to interest expense over the 18 month loan conversion period. During the years ended December 31, 2017 and 2016, the Company recorded a total of $75 and $300 of interest expense, respectively, related to the front end fees. Additionally, back end fees of $450 were amortized to interest expense over the 18 month loan conversion period of which $90 and $300 have been recorded as interest expense and as an increase in the carrying amount of the Notes during the years ended December 31, 2017 and 2016, respectively. The Company also incurred $265 in debt issuance costs during the year ended December 31, 2015 which were amortized to interest expense over the 18 month loan conversion period.

As of December 31, 2017, none of the Notes were outstanding.

Long-term Debt

On December 29, 2017, the Company entered into a Senior Secured Note Purchase Agreement (the Senior Secured Notes) with Athyrium Opportunities III Acquisition LP. The Senior Secured Notes provided the Company with up to $100,000 in capital, of which $75,000 was issued immediately. The remaining $25,000 (the Delayed Draw Notes) may be issued between April 1, 2019 and August 14, 2019, subject to the Company achieving trailing four quarter net revenues (as calculated pursuant to the terms of the Note Purchase Agreement) of $15,000 and a pro forma ratio of total debt to trailing four quarter net revenues not exceeding 6.50 to 1.00, and certain other conditions.

The Senior Secured Notes bear interest at 9.0% plus the three-month London Inter-bank Offered Rate (LIBOR) rate, subject to a 1.0% floor and are scheduled to mature on June 29, 2023. The interest rate was 10.75% at December 31, 2017. The Senior Secured Notes bore front-end fees of 1% of the aggregate principal amount, which were paid at issuance. The Company is also required to pay an exit fee of 2% of any principal payments (whether mandatory, voluntary, or at maturity) made throughout the term of the note purchase agreement.

The Company is required to make quarterly, interest only payments until the maturity date. The Company may make voluntary prepayments of the Senior Secured Notes, in whole or in part, and subject to certain exceptions, is required to make mandatory prepayments upon the occurrence of certain events as defined in the agreement, including, the occurrence of a change of control.

All mandatory and voluntary prepayments of the Senior Secured Notes are subject to the payment of prepayment premiums as follows: (i) if prepayment occurs prior to the second anniversary of the applicable date of issuance, an amount equal to the amount by which (a) the present value of 102% of the principal prepaid plus all interest that would have accrued on such principal through such second anniversary exceeds (b) the amount of principal prepaid, (ii) if prepayment occurs on or after the second anniversary of the applicable date of issuance but prior to the third anniversary of such issuance, an amount equal to 2% of the principal prepaid, and (iii) if prepayment occurs on or after the third anniversary of the applicable date of issuance but prior to the fourth anniversary of such issuance, an amount equal to 1% of the principal prepaid. No prepayment premium is due on any principal prepaid after the fourth anniversary of the applicable date of issuance of any Senior Secured Notes.

The Senior Secured Notes are secured by a pledge of substantially all of the Company’s assets and contains affirmative and negative covenants customary for financings of this type, including limitations on the Company’s and its subsidiaries’ ability to, among other things, incur additional debt, grant or permit additional liens, make investments and acquisitions, merge or consolidate with others, dispose of assets, grant certain license rights related to the Company's products, technology and other intellectual property rights, pay dividends and distributions, repay junior indebtedness and enter into affiliate transactions, in each case, subject to certain exceptions. In addition, the Senior Secured Notes contains financial covenants requiring the Company to maintain (i) at least $10,000 of cash and cash equivalents and (ii) following the issuance of the Delayed Draw Notes or upon entering into certain exclusive licenses of XHANCE, a total debt to trailing four quarter net revenue ratio of less than 6.50 to 1.00 initially, and thereafter declining quarterly by equal half-steps to a ratio of less than 3.00 to 1.00. As of December 31, 2017, the Company was in compliance with the covenants.

The Company recorded interest expense of $48 during the year ended December 31, 2017, in conjunction with the Senior Secured Notes. Interest expense included total coupon interest, back end fees, front end fees and the amortization of debt issuance costs. The front-end fees of $1,000 were recorded as debt discount at issuance and are being amortized to interest expense over the 5.5 year term of the loan. Additionally, back end fees of $2,000 are being amortized to interest expense and are recorded as, an increase in the carrying amount throughout the term of the Senior Secured Notes. The Company also incurred $2,140 in debt issuance costs during the year ended December 31, 2017 which are also being amortized to interest expense over the term of the Senior Secured Notes.

As of December 31, 2017, the long-term debt balance is comprised of the following:



	December 31,
	2017
Face amount	$	75,000
Front end fees	(999		)
Debt issuance costs	(2,139		)
Back end fees	1
Long-term debt, net	$	71,863

Long-Term Debt

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Long-Term Debt

Convertible Notes

At December 31, 2017 and 2016, the Company's convertible notes payable, net, balance was as follows:



	December 31,
	2017		2016
Face amount	$	—	$	15,000
Front end fees	—		(75		)
Debt issuance costs	—		(44		)
Back end fees	—		375
Convertible notes payable, net	$	—	$	15,256

As of December 31, 2016, the fair value of the Notes was $21,814, which was estimated based on the as converted value of the Notes as of that date.

As of December 31, 2017, none of the Notes were outstanding.

Long-term Debt

As of December 31, 2017, the long-term debt balance is comprised of the following:



	December 31,
	2017
Face amount	$	75,000
Front end fees	(999		)
Debt issuance costs	(2,139		)
Back end fees	1
Long-term debt, net	$	71,863

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans For US employees, the Company maintains a defined contribution 401(k) retirement plan, which covers all employees. Employees are eligible on the first of the month following their date of hire. Under the 401(k) retirement plan, participating employees may defer up to 100% of their pre-tax salary but not more than statutory limits. In October 2017, the Company adopted a 401(k) matching program for its US employees. The Company matches 100% of the first 3% of participating employee contributions and 50% of the next 2% of participating employee contributions, subject to applicable IRC limits. For 2017, the 401(k) match was applied to eligible earnings starting January 1, 2017. As of December 31, 2017, approximately $230 related to the Company match applicable to 2017 employee contributions, which Company match will be made in the first quarter of 2018.There were no contributions to the plan by the Company in the years ended December 31, 2016 or 2015. The Company's contributions are made in cash. The Company's common stock is not currently an investment option available to participants in the 401(k) retirement plan. For Norway and UK employees, the Company maintains defined contribution pension plans which meet statutory requirements of those jurisdictions. The Company incurred costs of $45, $24 and $24 related to the pension plans for the years ended December 31, 2017, 2016 and 2015, respectively.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Leases

The Company leases office space under four operating leases. Rent expense is recognized as incurred.

The following is a schedule of future minimum annual payments as of December 31, 2017 under non-cancellable operating lease agreements:



For the years ending December 31:
2018	187
Total future minimum lease payments as of December 31, 2017	$	187

Rent expense under these operating leases was $689, $407 and $312 for the years ended December 31, 2017, 2016 and 2015, respectively.

In January 2018, the Company amended its existing office lease agreement for the Company’s headquarters in Yardley, PA (the Lease Amendment). Under the terms of the Lease Amendment, the Company’s leased office space was increased from approximately 20,050 square feet to approximately 30,000 square feet, and the term of the lease was extended from March 31, 2018 to May 31, 2021 (the Extended Term), with an option to renew the lease for an additional three-year term. The Company’s rent payments during the Extended Term will be approximately $2,750 in the aggregate, and the Company will also be required to pay its proportionate share of certain operating costs and property taxes applicable to the leased premises.

Purchase commitments

In November 2017, the Company entered into agreement with a contract sales organization for the recruitment, deployment and management of a contract sales force to market XHANCE in the US. Subject to certain limited exceptions, the Company may not terminate this agreement until after the first anniversary of the deployment of the sales force (which occurred in March 2018). The Company estimates the expenses related to the non-cancellable services during this period to be approximately $16,354. Thereafter, the Company may terminate the agreement subject to potential early termination fees ranging from $100 to $700.

As of December 31, 2017, the Company had no other outstanding non-cancellable purchase commitments related to inventory and other goods and services, including pre-commercial manufacturing scale-up and sales and marketing activities.

Employment agreements

The Company has entered into employment contracts with its officers and certain employees that provide for severance and continuation of benefits in the event of termination of employment by the Company without cause or by the employee for good reason. In addition, in the event of termination of employment following a change in control, the vesting of certain equity awards may be accelerated.

Litigation

Liabilities for loss contingencies arising from claims, assessments, litigation, fines, penalties, and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. There are no matters currently outstanding.

Stockholders' equity (deficit)	12 Months Ended
Stockholders' equity (deficit)	Dec. 31, 2017
Equity [Abstract]
Stockholders' equity (deficit)	Stockholders' equity (deficit) Common stock In October 2017, the Company increased the number of authorized common shares from 10,624,486 to 200,000,000 and completed an initial public offering (IPO) of its common stock, selling 8,625,000 shares at $16.00 per share. As a result of the IPO, the Company received $125,471 in net proceeds, after deducting discounts and commissions of $9,660 and offering expenses of approximately $2,869 payable by the Company. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Subject to preferences that may apply to any outstanding preferred stock, holders of common stock are entitled to receive ratably any dividends that the Company’s board of directors may declare out of funds legally available for that purpose on a non-cumulative basis. No dividends had been declared through December 31, 2017. Common stock warrants As of December 31, 2017, the Company had 1,890,489 warrants outstanding to purchase shares of the Company's common stock with an exercise price of $8.16. The warrants expire on November 1, 2020. Redeemable convertible preferred stock During the year ended December 31, 2017, the Company sold 1,117,578 shares of Series D Preferred Stock at a per share purchase price of $32.85, resulting in gross proceeds to the Company of $36,712 (the Series D Financing). In connection with the Series D Financing, the Company's existing convertible notes and associated accrued interest and back end fees thereon totaling $19,527 converted into 687,474 shares of Series C-2 Preferred Stock at a per share conversion price of approximately $28.40 (Note 8). In conjunction with the Series D financing, the number of authorized shares of common stock was increased from 10,624,486 to 13,067,149 and the number of authorized shares of preferred stock was increased from 6,875,514 to 8,932,851, of which 1,369,863 shares were designated as Series D shares and 687,474 shares were designated as Series C-2 shares. Also, the redemption date for all classes of the Company's preferred stock was extended to March 24, 2020 and the terms upon which all classes of Preferred Stock would mandatorily convert into common stock in connection with an underwritten public offering were revised to align with the terms of the Series C-2 preferred stock. Upon consummation of the IPO in October 2017, all of the outstanding shares of the Company's redeemable convertible preferred stock were converted into an aggregate of 25,068,556 shares of common stock. In connection with the IPO, 5,000,000 shares of preferred stock, with a par value of $0.001 per share, were authorized for issuance. As of December 31, 2017, no preferred stock was issued or outstanding.

Stock-based Compensation

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-based Compensation

Stock-based compensation

The Company issues stock-based awards pursuant to its 2010 Stock Incentive Plan. Effective as of October 12, 2017, the Company's 2010 Stock Incentive Plan was amended and restated(A&R Plan). The A&R Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units, deferred stock units, performance shares, stock appreciation rights and other equity-based awards. The Company's employees, officers, directors and other persons are eligible to receive awards under the A&R Plan. As of December 31, 2017, 6,894,445 shares of the Company's common stock were authorized to be issued under the A&R Plan, and 546,131 shares were reserved for future awards under the A&R Plan. The number of shares of the Company's common stock authorized under the A&R Plan will automatically increase on January 1st of each year, commencing on January 1, 2018 and continuing until the expiration of the A&R Plan, in an amount equal to four percent of the total number of shares of the Company's common stock outstanding on December 31st of the preceding calendar year, subject to the discretion of the Company's board of directors or compensation committee to determine a lesser number of shares shall be added for such year.

The amount, terms of grants, and exercisability provisions are determined and set by the Company's board of directors or compensation committee. The Company measures employee stock-based awards at grant-date fair value and records compensation expense on a straight-line basis over the vesting period of the award. Stock-based awards issued to non-employees are revalued until the award vests.

Service-based stock options

Options issued under the A&R Plan generally have a contractual life of up to 10 years and may be exercisable in cash or as otherwise determined by the board of directors. Vesting generally occurs over a period of not greater than four years. The following table summarizes the activity related to service-based stock option grants to employees and nonemployees for the years ended December 31, 2017:



	Shares		Weighted average exercise price per share		Weighted average remaining contractual life
Outstanding at December 31, 2016	1,894,083		$	3.09	6.67
Granted	2,341,096		14.00
Exercised	(26,047	)	2.34
Expired	(2,887	)	5.68
Forfeited	(96,036	)	9.29
Outstanding at December 31, 2017	4,110,209		$	9.16	7.89
Exercisable at December 31, 2017	1,327,843		$	2.36	4.53
Vested and expected to vest at December 31, 2017	4,110,209		$	9.16	7.89

During the year ended December 31, 2017,time-based options to purchase 2,341,096 shares of common stock were granted to employees that generally vest over four years. The options had an estimated weighted average grant date fair value of $9.68. The grant date fair value of each option grant was estimated at the time of grant using the Black-Scholes option-pricing model.

The total aggregate intrinsic value of service-based options exercised during the years ended December 31, 2017 and 2016 was $435 and $20, respectively. There were no service-based options exercised during the year ended December 31, 2015. The aggregate intrinsic value of service-based options outstanding and service-based options exercisable as of December 31, 2017 was $40,102 and $21,961, respectively. At December 31, 2017, the unrecognized compensation cost related to unvested service-based stock options expected to vest was $22,198. This unrecognized compensation will be recognized over an estimated weighted-average amortization period of 3.89 years.

Performance-based stock options

The Company has issued performance-based stock options under the A&R Plan which generally have a ten-year life from the date of grant and may vest upon the achievement of certain milestones in connection with the Company's development programs. Additionally, the Company has issued options in excess of the fair market value of common shares on the issuance date that are only exercisable upon a change in control or upon or after an initial public offering. Compensation expense for performance-based stock options is only recognized when management determines it is probable that the awards will vest.

The following table summarizes the activity related to performance-based stock option grants to employees and nonemployees for the years ended December 31, 2017:



	Shares		Weighted average exercise price per share		Weighted average remaining contractual life
Outstanding at December 31, 2016	2,171,760		$	9.59	6.55
Granted	—		—
Exercised	(30,393	)	2.44
Forfeited	—		—
Outstanding at December 31, 2017	2,141,367		$	9.69	5.56
Exercisable at December 31, 2017	1,708,181		$	8.02	5.04
Vested and expected to vest at December 31, 2017	2,141,367		$	9.69	5.56

The total aggregate intrinsic value of performance-based options exercised during the years ended December 31, 2017 and 2016 was $505 and $20 respectively. There were no performance-based options exercised during the year ended December 31, 2015. The aggregate intrinsic value of performance-based options outstanding and performance-based options exercisable as of December 31, 2017 was $19,713 and $18,592, respectively. As of December 31, 2017, there was $563 of unrecognized compensation cost related to unvested performance-based stock options that will vest and be expensed over an estimated weighted average amortization period of 2.68 years.

2017 Employee Stock Purchase Plan

The Company's 2017 Employee Stock Purchase Plan (the 2017 Plan) became effective on October 12, 2017. The 2017 Plan authorized the issuance of up to 144,395 shares of the Company's common stock pursuant to purchase rights granted to its employees or to employees of any of its participating affiliates. The number of shares of the Company's common stock that may be issued pursuant to rights granted under the 2017 Plan shall automatically increase on January 1st of each year, commencing on January 1, 2018 and continuing until the expiration of the 2017 Plan, in an amount equal to one percent of the total number of shares of the Company's common stock outstanding on December 31st of the preceding calendar year, subject to the discretion of the board of directors or compensation committee to determine a lesser number of shares shall be added for such year.

Under the 2017 Plan, eligible employees can purchase the Company’s common stock through accumulated payroll deductions at such times as are established by the administrator. The 2017 Plan is administered by the compensation committee. Under the 2017 Plan, eligible employees may purchase the Company’s common stock at discount of up to 85% of the lower of the fair market value of the Company's common stock on the first day of the offering period or on the last day of the offering period. Eligible employees may contribute up to 15% of their eligible compensation. Under the 2017 Plan, a participant may not accrue rights to purchase more than $25,000 worth of the Company’s common stock for each calendar year in which such right is outstanding.

Effective October 12, 2017, employees who elected to participate in the 2017 Plan commenced payroll withholdings that accumulate through June 30, 2018. Beginning on January 1, 2018, employees who elected to participate in the 2017 Plan will commence payroll withholdings that accumulate through June 30, 2018.

At the end of each of the current offering periods, shares of the Company’s common stock may be purchased at 85% of the lower of the fair market value of the Company’s common stock on the first or last day of the respective offering period. In accordance with the guidance in ASC 718-50 – Compensation – Stock Compensation, the ability to purchase shares of the Company’s common stock at the lower of the price on the first day of the offering period or the last day of the offering period (i.e. the purchase date) represents an option and, therefore, the 2017 Plan is a compensatory plan under this guidance. Accordingly, stock-based compensation expense is determined based on the option’s grant-date fair value as estimated by applying the Black Scholes option-pricing model and is recognized over the requisite service period of the option. The Company has recognized stock-based compensation expense of $106 during the year ended December 31, 2017 related to the 2017 Plan.

Stock-based compensation expense

The Company recorded stock-based compensation expense in the following expense categories of its accompanying consolidated statements of operations for the years ended December 31, 2017 and 2016:



	Year ended December 31,
	2017		2016		2015
Research and development	$	1,288	$	362	$	354
General and administrative	3,808		237		234
Total stock-based compensation expense	$	5,096	$	599	$	588

The Company utilized the Black-Scholes valuation model for estimating the fair value of stock options granted and the option component of the 2017 Plan. The Company calculated the fair value of each option grant and the option component of the 2017 Plan on the respective dates of grant using the following weighted average assumptions:



	2010 A&R Stock Incentive Plan		2017 Employee Stock Purchase Plan
	December 31,		December 31,
	2017		2017
Risk free interest rate	2.06	%	1.27	%
Expected term (in years)	6.06		0.72
Expected volatility	78.67	%	91.18	%
Annual dividend yield	0.00	%	0.00	%

Option valuation methods, including Black-Scholes, require the input of subjective assumptions, which are discussed below.

•

The expected term of employee options is determined using the "simplified" method, as prescribed in SEC's Staff Accounting Bulletin (SAB) No. 107, whereby the expected life equals the arithmetic average of the vesting term and the original contractual term of the option due to the Company's lack of sufficient historical data. The expected term of nonemployee options is equal to the contractual term.


•	The expected volatility is based on historical volatilities of similar entities within the Company's industry which were commensurate with the expected term assumption as described in SAB No. 107.


•	The risk-free interest rate is based on the interest rate payable on US Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected term.


•	The expected dividend yield is 0% because the Company has not historically paid, and does not expect for the foreseeable future to pay, a dividend on its common stock.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

Income taxes

The Tax Cuts and Jobs Act, or the TCJA, was enacted on December 22, 2017 and became effective January 1, 2018. Among other changes, the TCJA significantly lowers the US corporate income tax rate, implements a territorial tax system and imposes a one-time transition tax on deemed repatriated earnings of foreign subsidiaries.

The TCJA reduces the US corporate income tax rate from 35% to 21%, effective January 1, 2018. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to reverse. As a result of the reduction in the US corporate income tax rate, the Company revalued its net deferred tax assets at December 31, 2017. Due to the full valuation allowance on the Company's deferred tax assets, no tax expense or benefit associated with the re-measurement was recognized in the Company's consolidated statement of operations for the year ended December 31, 2017. The change in the US corporate tax rate is also included in the Company’s deferred tax table.

The TCJA provided for a one-time transition tax on the deemed repatriation of post-1986 undistributed foreign subsidiary earnings and profits, or E&P. As the Company's foreign subsidiaries did not have consolidated accumulated E&P, the Company did not record any income tax expense related to the transition tax.

Due to the timing of and the substantial changes made by the TCJA , the Staff of the Securities and Exchange Commission, or the SEC, issued Staff Accounting Bulletin No. 118, or SAB 118, which provides registrants a measurement period to report the impact of the new US tax law. During the measurement period, provisional amounts for the effects of the law are recorded to the extent a reasonable estimate can be made. To the extent that all information necessary is not available, prepared or analyzed, companies may recognize provisional estimated amounts for a period of up to one year following enactment of the TCJA. Accordingly, the Company's preliminary estimate of the impact of the TCJA and the re-measurement of its deferred tax assets and liabilities is subject to finalization of its analysis of certain matters, such as developing interpretations of the TCJA provisions, changes to certain estimates and the filing of its tax returns. US Treasury regulations, administrative interpretations or court decisions interpreting the TCJA may require adjustments to the Company's initial estimates. The final determination of the TCJA provisions and re-measurement of the Company's deferred tax assets and liabilities will be completed as additional information becomes available, but no later than one year from the enactment of the TCJA.

Income taxes have been recorded on the following income (loss) before income tax expense:



	Year ended December 31,
	2017			2016
Domestic operations	$	(30,463	)	$	(4,967	)
Foreign operations	(18,439		)	27,580
Income (loss) before provision for income taxes	$	(48,902	)	$	22,613

A reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes as reflected in the financial statements is as follows:



	Year ended December 31,
	2017		2016
Income tax expense at statutory rate	35.0	%	35.0	%
Permanent items	0.5		—
Foreign rate differential	(4.2	)	(12.2	)
State taxes, net of federal benefit	0.8		(1.4	)
Tax rate changes	(15.4	)	—
Change in valuation allowance	(16.7	)	(21.4	)
Effective income tax rate	0.0	%	0.0	%

Tax rate changes includes both the impact of the reduction in the US tax rate under the TCJA and a reduction in the Norway tax rate.

The principal components of the Company’s deferred tax assets and liabilities were as follows:



	Year ended December 31,
	2017			2016
Deferred tax assets:
Accrued expenses and other	$	972		$	539
Fixed assets	55			—
Interest expense	783			677
Stock compensation	1,701			1,092
Research and development	2,485			2,183
Net operating losses	29,636			22,695
Total deferred tax assets	35,632			27,186
Deferred tax liabilities:
Fixed assets	—			(46		)
Total deferred tax liabilities:	—			(46		)
Less: Valuation allowance	(35,632		)	(27,140		)
Total net deferred tax assets (liabilities)	$	—		$	—

The TCJA, in addition to the changes indicated above, contained other provisions that may have a future impact on the Company. The provisions include limitations on the deductibility of interest based on the amount of adjusted taxable income, the deferral of research and development deductions, the acceleration of deductions related to fixed asset additions, changes to the utilization of net operating loss carry forwards and changes in the carry forward period, and global intangible low-taxed income provisions that subject foreign subsidiary income that exceeds an allowable return to current US taxation.

As of December 31, 2017, the Company had foreign net operating loss, or NOL, carry forwards of $96,616 primarily from its operations in Norway. As of December 31, 2017, the Company had federal and state NOL’s of $30,327 and $13,702, respectively. These domestic NOL carry forwards may be subject to an annual limitation in the event of cumulative changes in the ownership interest of significant stockholders over a three‑year period in excess of 50%. This could limit the amount of NOLs that the Company can utilize annually to offset future domestic taxable income or tax liabilities, if any. The amount of the annual limitation, if any, will be determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The federal and state NOL’s will expire beginning in 2030 and through 2037.

ASC 740 requires a valuation allowance to reduce the deferred tax assets reported if, based on the weight of available evidence, it is more likely than not that all or a portion of the deferred tax assets will not be realized. After consideration of all the evidence, both positive and negative, the Company has recorded a full valuation allowance against its deferred tax assets at December 31, 2017 and 2016, respectively, because the Company’s management has determined that is it more likely than not that these assets will not be fully realized. The Company experienced a net change in valuation allowance of $8,492 during the year ended December 31, 2017.

The Company files income tax returns in Norway, the UK, the US, and various states. The Company is subject to examination by federal, state and foreign jurisdictions. The Company’s tax years in the US are open under statute from inception to present. All open years may be examined to the extent that tax credit or net operating loss carryforwards are used in future periods.

The Company’s policy is to record interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2017, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s statement of operations.

Quarterly Financial Information (unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information (unaudited)

16. Quarterly Financial Information (unaudited)

The following table summarizes the unaudited consolidated financial results of operations for the quarters ended (amounts in thousands except per share data):



	2017 Quarters Ended
	March 31,			June 30,			September 30,			December 31,
Revenues	$	—		$	—		$	—		$	—
Research and development	3,073			5,906			6,641			1,212
Selling, general and administrative	4,230			2,431			6,553			18,484
Total operating expenses	7,303			8,337			13,194			19,696
Income (loss) from operations	(7,303		)	(8,337		)	(13,194		)	(19,696		)
Net income (loss)	(8,075		)	(8,208		)	(13,068		)	(19,551		)
Net income (loss) attributable to common stockholders	(11,671		)	(12,836		)	(17,192		)	(20,268		)
Basic net income (loss) per common share	$	(2.87	)	$	(3.16	)	$	(4.23	)	$	(0.64	)
Diluted net income (loss) per common share	$	(2.87	)	$	(3.16	)	$	(4.23	)	$	(0.64	)



	2016 Quarters Ended
	March 31,		June 30,			September 30,			December 31,
Revenues	$	47,500	$	—		$	—		$	—
Research and development	4,961		3,412			3,868			3,070
Selling, general and administrative	2,250		1,046			1,761			1,812
Total operating expenses	7,211		4,458			5,629			4,882
Income (loss) from operations	40,289		(4,458		)	(5,629		)	(4,882		)
Net income (loss)	39,572		(5,265		)	(6,106		)	(5,588		)
Net income (loss) attributable to common stockholders	36,294		(8,544		)	(9,385		)	(8,866		)
Basic net income (loss) per common share	$	1.52	$	(2.10	)	$	(2.32	)	$	(2.18	)
Diluted net income (loss) per common share	$	1.25	$	(2.10	)	$	(2.32	)	$	(2.18	)

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Principles of consolidation

Use of estimates

Cash and cash equivalents

The Company maintains its cash and cash equivalent balances at foreign and domestic financial institutions.

Fair value of financial instruments


•	Level 1 — Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities.


•	Level 2 — Valuations based on observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.


•	Level 3 — Valuations based on inputs that are unobservable and models that are significant to the overall fair value measurement.

The Company's financial instruments also included convertible debt at December 31, 2016 (Note 8).

Inventory

Property and equipment

Conversely, deposits on equipment received after the September 18, 2017 FDA approval of XHANCE were capitalized as fixed assets when the equipment was received and therefore classified as long-term deposits at December 31, 2017.

Long lived assets

Revenue recognition

Advertising expenses

The Company expenses the costs of advertising, including promotional expenses, as incurred.

Research and development expense

Research and development

For equipment received prior to FDA approval, the Company recorded the cost associated with the equipment purchase as a component of research and development expense if there was no alternative future use of the equipment without FDA approval.

Stock-based compensation

Income taxes

Net income (loss) per common share

Recent accounting pronouncements

The Company plans to adopt the new standard effective January 1, 2018 using the modified retrospective approach.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Inventory

Inventory consisted of the following:



	December 31,
	2017		2016
Raw materials	$	1,385	$	—
Work-in-process	628		—
Finished goods	—		—
Total	$	2,013	$	—

Property and equipment

The estimated useful lives of equipment are as follows:



Computer equipment	3 years
Software	3 years
Machinery & production equipment	5-10 years
Furniture & fixtures	3-5 years
Leasehold improvements	Shorter of lease term or useful life

Property and equipment, net, consisted of:



	December 31,
	2017			2016
Computer equipment and software	$	307		$	293
Furniture and fixtures	89			121
Machinery and equipment	2,495			255
Leasehold improvements	28			28
	2,919			697
Less: accumulated depreciation	(355		)	(374		)
	$	2,564		$	323

Computation of basic and diluted net income (loss) per share

The following table sets forth the computation of basic and diluted net income (loss) per share for the periods indicated:



	Year Ended December 31,
	2017			2016			2015
Basic net (loss) income per common share calculation:
Net (loss) income attributable to common stockholders	$	(61,967	)	$	9,499		$	(40,375	)
Less: undistributed earnings to participating securities	—			(7,884		)	—
Net (loss) income attributable to common stockholders — basic	(61,967		)	1,615			(40,375		)
Weighted average common shares outstanding — basic	10,999,121			4,054,316			4,049,668
Net (loss) income per share of common stock — basic	$	(5.63	)	$	0.40		$	(9.97	)
Diluted net (loss) income per common share calculation:
Net (loss) income attributable to common stockholders	$	(61,967	)	$	9,499		$	(40,375	)
Less: undistributed earnings to participating securities	—			(7,884		)	—
Net (loss) income attributable to common stockholders — diluted	(61,967		)	1,615			(40,375		)
Weighted average common shares outstanding — basic	10,999,121			4,054,316			4,049,668
Stock options	—			925,865			—
Weighted average common shares outstanding — diluted	10,999,121			4,980,181			4,049,668
Net (loss) income per share of common stock — diluted	$	(5.63	)	$	0.32		$	(9.97	)

Schedule of antidilutive shares excluded from earnings per share

Diluted net income (loss) per common share for the periods presented do not reflect the following potential common shares, as the effect would be antidilutive:



	Year Ended December 31,
	2017	2016	2015
Stock options	2,141,367	2,346,073	3,413,178
Common stock warrants	1,890,489	1,890,489	1,890,489
Convertible debt	—	1,917,522	1,888,484
Convertible preferred stock	—	19,855,772	19,855,772
Total	4,031,856	26,009,856	27,047,923

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property and Equipment

The estimated useful lives of equipment are as follows:



Computer equipment	3 years
Software	3 years
Machinery & production equipment	5-10 years
Furniture & fixtures	3-5 years
Leasehold improvements	Shorter of lease term or useful life

Property and equipment, net, consisted of:



	December 31,
	2017			2016
Computer equipment and software	$	307		$	293
Furniture and fixtures	89			121
Machinery and equipment	2,495			255
Leasehold improvements	28			28
	2,919			697
Less: accumulated depreciation	(355		)	(374		)
	$	2,564		$	323

Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

As of December 31, 2017, the long-term debt balance is comprised of the following:



	December 31,
	2017
Face amount	$	75,000
Front end fees	(999		)
Debt issuance costs	(2,139		)
Back end fees	1
Long-term debt, net	$	71,863

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21521-112644

+ Details

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Lessee, Operating Lease

The following is a schedule of future minimum annual payments as of December 31, 2017 under non-cancellable operating lease agreements:



For the years ending December 31:
2018	187
Total future minimum lease payments as of December 31, 2017	$	187

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of stock option activity

The following table summarizes the activity related to performance-based stock option grants to employees and nonemployees for the years ended December 31, 2017:



	Shares		Weighted average exercise price per share		Weighted average remaining contractual life
Outstanding at December 31, 2016	2,171,760		$	9.59	6.55
Granted	—		—
Exercised	(30,393	)	2.44
Forfeited	—		—
Outstanding at December 31, 2017	2,141,367		$	9.69	5.56
Exercisable at December 31, 2017	1,708,181		$	8.02	5.04
Vested and expected to vest at December 31, 2017	2,141,367		$	9.69	5.56

The following table summarizes the activity related to service-based stock option grants to employees and nonemployees for the years ended December 31, 2017:



	Shares		Weighted average exercise price per share		Weighted average remaining contractual life
Outstanding at December 31, 2016	1,894,083		$	3.09	6.67
Granted	2,341,096		14.00
Exercised	(26,047	)	2.34
Expired	(2,887	)	5.68
Forfeited	(96,036	)	9.29
Outstanding at December 31, 2017	4,110,209		$	9.16	7.89
Exercisable at December 31, 2017	1,327,843		$	2.36	4.53
Vested and expected to vest at December 31, 2017	4,110,209		$	9.16	7.89

Schedule of allocated stock-based compensation expense

The Company recorded stock-based compensation expense in the following expense categories of its accompanying consolidated statements of operations for the years ended December 31, 2017 and 2016:



	Year ended December 31,
	2017		2016		2015
Research and development	$	1,288	$	362	$	354
General and administrative	3,808		237		234
Total stock-based compensation expense	$	5,096	$	599	$	588

Schedule of fair value options using Black-Scholes pricing model

The Company calculated the fair value of each option grant and the option component of the 2017 Plan on the respective dates of grant using the following weighted average assumptions:



	2010 A&R Stock Incentive Plan		2017 Employee Stock Purchase Plan
	December 31,		December 31,
	2017		2017
Risk free interest rate	2.06	%	1.27	%
Expected term (in years)	6.06		0.72
Expected volatility	78.67	%	91.18	%
Annual dividend yield	0.00	%	0.00	%

The Company calculated the fair value of each option grant and the option component of the 2017 Plan on the respective dates of grant using the following weighted average assumptions:



	2010 A&R Stock Incentive Plan		2017 Employee Stock Purchase Plan
	December 31,		December 31,
	2017		2017
Risk free interest rate	2.06	%	1.27	%
Expected term (in years)	6.06		0.72
Expected volatility	78.67	%	91.18	%
Annual dividend yield	0.00	%	0.00	%

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of Income before Income Tax, Domestic and Foreign

Income taxes have been recorded on the following income (loss) before income tax expense:



	Year ended December 31,
	2017			2016
Domestic operations	$	(30,463	)	$	(4,967	)
Foreign operations	(18,439		)	27,580
Income (loss) before provision for income taxes	$	(48,902	)	$	22,613

Schedule of Effective Income Tax Rate Reconciliation

A reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes as reflected in the financial statements is as follows:



	Year ended December 31,
	2017		2016
Income tax expense at statutory rate	35.0	%	35.0	%
Permanent items	0.5		—
Foreign rate differential	(4.2	)	(12.2	)
State taxes, net of federal benefit	0.8		(1.4	)
Tax rate changes	(15.4	)	—
Change in valuation allowance	(16.7	)	(21.4	)
Effective income tax rate	0.0	%	0.0	%

Schedule of Deferred Tax Assets and Liabilities

The principal components of the Company’s deferred tax assets and liabilities were as follows:



	Year ended December 31,
	2017			2016
Deferred tax assets:
Accrued expenses and other	$	972		$	539
Fixed assets	55			—
Interest expense	783			677
Stock compensation	1,701			1,092
Research and development	2,485			2,183
Net operating losses	29,636			22,695
Total deferred tax assets	35,632			27,186
Deferred tax liabilities:
Fixed assets	—			(46		)
Total deferred tax liabilities:	—			(46		)
Less: Valuation allowance	(35,632		)	(27,140		)
Total net deferred tax assets (liabilities)	$	—		$	—

Quarterly Financial Information (unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information

The following table summarizes the unaudited consolidated financial results of operations for the quarters ended (amounts in thousands except per share data):



	2017 Quarters Ended
	March 31,			June 30,			September 30,			December 31,
Revenues	$	—		$	—		$	—		$	—
Research and development	3,073			5,906			6,641			1,212
Selling, general and administrative	4,230			2,431			6,553			18,484
Total operating expenses	7,303			8,337			13,194			19,696
Income (loss) from operations	(7,303		)	(8,337		)	(13,194		)	(19,696		)
Net income (loss)	(8,075		)	(8,208		)	(13,068		)	(19,551		)
Net income (loss) attributable to common stockholders	(11,671		)	(12,836		)	(17,192		)	(20,268		)
Basic net income (loss) per common share	$	(2.87	)	$	(3.16	)	$	(4.23	)	$	(0.64	)
Diluted net income (loss) per common share	$	(2.87	)	$	(3.16	)	$	(4.23	)	$	(0.64	)



	2016 Quarters Ended
	March 31,		June 30,			September 30,			December 31,
Revenues	$	47,500	$	—		$	—		$	—
Research and development	4,961		3,412			3,868			3,070
Selling, general and administrative	2,250		1,046			1,761			1,812
Total operating expenses	7,211		4,458			5,629			4,882
Income (loss) from operations	40,289		(4,458		)	(5,629		)	(4,882		)
Net income (loss)	39,572		(5,265		)	(6,106		)	(5,588		)
Net income (loss) attributable to common stockholders	36,294		(8,544		)	(9,385		)	(8,866		)
Basic net income (loss) per common share	$	1.52	$	(2.10	)	$	(2.32	)	$	(2.18	)
Diluted net income (loss) per common share	$	1.25	$	(2.10	)	$	(2.32	)	$	(2.18	)

Organization and Description of Business (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsidiary, Sale of Stock [Line Items]
Proceeds from the sale of common stock units in connection with initial public offering		$ 138,000	$ 0	$ 0
IPO
Subsidiary, Sale of Stock [Line Items]
Price per share (usd per share)	$ 16.00
Proceeds from the sale of common stock units in connection with initial public offering	$ 125,471
Fees and commissions	9,660
Stock issuance costs	$ 2,869
Common Stock \| IPO
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)	8,625,000
Conversion at Consummation of IPO \| Common Stock
Subsidiary, Sale of Stock [Line Items]
Shares issued, conversion of stock (in shares)	25,068,556

Liquidity (Details) - USD ($)	1 Months Ended	12 Months Ended
Liquidity (Details) - USD ($)	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 29, 2017
Subsidiary, Sale of Stock [Line Items]
Cash and cash equivalents		$ 234,854,000	$ 36,797,000
Proceeds from the sale of common stock units in connection with initial public offering		$ 138,000,000	0	$ 0
Redeemable Convertible Preferred Stock, Series D
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)		1,117,578
Proceeds from the sale of Series D preferred stock		$ 36,712,000	$ 0	$ 0
Price per share (usd per share)		$ 32.85
IPO
Subsidiary, Sale of Stock [Line Items]
Price per share (usd per share)	$ 16.00
Proceeds from the sale of common stock units in connection with initial public offering	$ 125,471,000
IPO \| Common Stock
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)	8,625,000
Note Purchase Agreement \| Senior Notes
Subsidiary, Sale of Stock [Line Items]
Unused borrowing capacity					$ 100,000,000
Face amount					$ 75,000,000

Summary of Significant Accounting Policies (Details) $ in Thousands		12 Months Ended
	Oct. 10, 2017	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Stock split conversion ratio	2.8879
Cash, uninsured amount		$ 233,772	$ 35,866
Advertising expense		$ 1,833	$ 26	$ 44

Summary of Significant Accounting Policies - Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Raw materials	$ 1,385	$ 0
Work-in-process	628	0
Finished goods	0	0
Total	$ 2,013	$ 0

Summary of Significant Accounting Policies - Property and equipment (Details)	12 Months Ended
	Dec. 31, 2017
Computer equipment
Property, Plant and Equipment [Line Items]
Useful life	3 years
Software
Property, Plant and Equipment [Line Items]
Useful life	3 years
Machinery and equipment \| Minimum
Property, Plant and Equipment [Line Items]
Useful life	5 years
Machinery and equipment \| Maximum
Property, Plant and Equipment [Line Items]
Useful life	10 years
Furniture and fixtures \| Minimum
Property, Plant and Equipment [Line Items]
Useful life	3 years
Furniture and fixtures \| Maximum
Property, Plant and Equipment [Line Items]
Useful life	5 years

Summary of Significant Accounting Policies - Basic and diluted net income (loss) per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic net (loss) income per common share calculation:
Net (loss) income	$ (19,551)	$ (13,068)	$ (8,208)	$ (8,075)	$ (5,588)	$ (6,106)	$ (5,265)	$ 39,572	$ (48,902)	$ 22,613	$ (28,314)
Net (loss) income attributable to common stockholders	$ (20,268)	$ (17,192)	$ (12,836)	$ (11,671)	$ (8,866)	$ (9,385)	$ (8,544)	$ 36,294	$ (61,967)	$ 9,499	$ (40,375)
Weighted average common shares outstanding — basic (in shares)									10,999,121	4,054,316	4,049,668
Net (loss) income per share of common stock — basic (in USD per share)	$ (0.64)	$ (4.23)	$ (3.16)	$ (2.87)	$ (2.18)	$ (2.32)	$ (2.10)	$ 1.52	$ (5.63)	$ 0.40	$ (9.97)
Diluted net (loss) income per common share calculation:
Net (loss) income	$ (19,551)	$ (13,068)	$ (8,208)	$ (8,075)	$ (5,588)	$ (6,106)	$ (5,265)	$ 39,572	$ (48,902)	$ 22,613	$ (28,314)
Weighted average common shares outstanding — diluted (in shares)									10,999,121	4,980,181	4,049,668
Net (loss) income per share of common stock — diluted (in USD per share)	$ (0.64)	$ (4.23)	$ (3.16)	$ (2.87)	$ (2.18)	$ (2.32)	$ (2.10)	$ 1.25	$ (5.63)	$ 0.32	$ (9.97)
Scenario, Adjustment
Basic net (loss) income per common share calculation:
Net (loss) income									$ (61,967)	$ 9,499	$ (40,375)
Less: undistributed earnings to participating securities									0	(7,884)	0
Net (loss) income attributable to common stockholders									$ (61,967)	$ 1,615	$ (40,375)
Weighted average common shares outstanding — basic (in shares)									10,999,121	4,054,316	4,049,668
Net (loss) income per share of common stock — basic (in USD per share)									$ (5.63)	$ 0.40	$ (9.97)
Diluted net (loss) income per common share calculation:
Net (loss) income									$ (61,967)	$ 9,499	$ (40,375)
Less: undistributed earnings to participating securities									0	(7,884)	0
Net (loss) income attributable to common stockholders — diluted									$ (61,967)	$ 1,615	$ (40,375)
Stock options (in shares)									0	925,865	0
Weighted average common shares outstanding — diluted (in shares)									10,999,121	4,980,181	4,049,668
Net (loss) income per share of common stock — diluted (in USD per share)									$ (5.63)	$ 0.32	$ (9.97)

Summary of Significant Accounting Policies - Antidilutive shares excluded from earnings per share (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of earnings per share	4,031,856	26,009,856	27,047,923
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of earnings per share	2,141,367	2,346,073	3,413,178
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of earnings per share	1,890,489	1,890,489	1,890,489
Convertible debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of earnings per share	0	1,917,522	1,888,484
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of earnings per share	0	19,855,772	19,855,772

Deposits and Other Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Short-term
Receivable due from the FDA	$ 0	$ 2,038
Deposits on equipment	0	1,201
Prepaid expenses and other	1,254	255
Total short-term deposits and other assets	1,254	3,494
Long-term
Deposits on equipment	329	499
Other	76	54
Total long-term deposits and other assets	405	553
Other Assets	$ 1,659	$ 4,047

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,919	$ 697
Less: accumulated depreciation	(355)	(374)
Property and equipment, net	2,564	323
Depreciation	164	83	$ 75
Disposed assets	209
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	307	293
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	89	121
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,495	255
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 28	$ 28

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Research and development expenses	$ 80	$ 736
Selling, general and administrative expenses	3,463	290
Bonus expense	4,163	1,390
Payroll and benefit expenses	633	125
Interest expense	45	0
Other	314	0
Accrued Liabilities, Current	$ 8,698	$ 2,541

AVP-825 License Agreement (Details) - License Agreement Terms - USD ($)	12 Months Ended		42 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate cash payments received from license agreement			$ 70,000,000
Potential proceeds upon achievement of milestones			$ 50,000,000
Licensing revenues	$ 0	$ 47,500,000

Convertible Notes (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2015
Debt Instrument [Line Items]
Debt issuance costs			$ (265)
Convertible notes payable, net	$ 0	$ 15,256
Convertible Debt
Debt Instrument [Line Items]
Face amount	0	15,000
Front end fees	0	(75)		$ (450)
Debt issuance costs	0	(44)
Back end fees	0	375
Convertible notes payable, net	$ 0	$ 15,256

Convertible Notes - Narrative (Details)				12 Months Ended
Convertible Notes - Narrative (Details)	Mar. 31, 2017 USD ($)	Mar. 24, 2017 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) tranche	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Interest expense, back end fees				$ 2,000,000
Debt issuance costs						$ 265,000
Convertible notes payable, net				0	$ 15,256,000
Convertible Debt
Debt Instrument [Line Items]
Face amount			$ 30,000,000
Number of tranches \| tranche			2
Stated interest rate			17.00%
Debt issuance costs			$ 450,000	0	75,000
Repayment increments			$ 100,000
Debt instrument, fair value					21,814,000
Interest expense, debt				862,000	3,517,000	$ 819,000
Coupon interest and back end fees				743,000	2,740,000
Loan conversion period			18 months
Interest expense, back end fees				90,000	300,000
Interest expense, front end fees				75,000	300,000
Back end fees				0	375,000
Debt issuance costs				0	44,000
Convertible notes payable, net				0	$ 15,256,000
Convertible Debt \| Tranche One
Debt Instrument [Line Items]
Face amount			$ 15,000,000
Convertible Debt \| Tranche Two
Debt Instrument [Line Items]
Face amount			$ 15,000,000
Conversion of Convertible notes into Series C2 Preferred Stock
Debt Instrument [Line Items]
Debt conversion, original debt amount				$ 19,527,000
Series D Financing \| Convertible Debt
Debt Instrument [Line Items]
Debt conversion, original debt amount		$ 19,527,000
Redeemable Convertible Preferred Stock, Series C2 \| Conversion of Convertible notes into Series C2 Preferred Stock
Debt Instrument [Line Items]
Debt conversion shares issued (in shares) \| shares		687,474		687,474
Debt conversion, price per share (usd per share) \| $ / shares		$ 28.40		$ 28.40
Maximum \| Conversion of Convertible notes into Series C2 Preferred Stock
Debt Instrument [Line Items]
Convertible debt	$ 300,000,000

Long-Term Debt - Narrative (Details)		4 Months Ended	12 Months Ended
Long-Term Debt - Narrative (Details)	Dec. 29, 2017 USD ($) quarter	Aug. 14, 2019 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Debt amortization period			5 years 6 months
Interest expense, back end fees			$ 2,000,000
Debt issuance costs			2,140,000
Senior Notes
Debt Instrument [Line Items]
Amortization of debt discount			$ 1,000,000
Senior Notes \| Note Purchase Agreement
Debt Instrument [Line Items]
Unused borrowing capacity	$ 100,000,000
Face amount	$ 75,000,000
Stated interest rate	9.00%		10.75%
Upfront fee	1.00%
Exit fee	2.00%
Covenant, cash and cash equivalents	$ 10,000,000
Interest expense, debt			$ 48,000
Unamortized debt issuance costs			$ 2,139,000
Senior Notes \| Note Purchase Agreement \| Prior to Second Anniversary
Debt Instrument [Line Items]
Redemption price rate	102.00%
Senior Notes \| Note Purchase Agreement \| On Or After Second Anniversary
Debt Instrument [Line Items]
Prepayment fee	2.00%
Senior Notes \| Note Purchase Agreement \| On Or After Third Anniversary
Debt Instrument [Line Items]
Prepayment fee	1.00%
Senior Notes \| Note Purchase Agreement \| After Fourth Anniversary
Debt Instrument [Line Items]
Prepayment fee	0.00%
Senior Notes \| Note Purchase Agreement \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate floor	1.00%
Senior Notes \| Note Purchase Agreement - Delayed Draw Notes
Debt Instrument [Line Items]
Unused borrowing capacity	$ 25,000,000
Number of trailing quarters \| quarter	4
Total debt to trailing quarter net sales ratio	6.50
Senior Notes \| Note Purchase Agreement - Delayed Draw Notes \| Minimum
Debt Instrument [Line Items]
Total debt to trailing quarter net sales ratio	3.00
Scenario, Forecast \| Senior Notes \| Note Purchase Agreement - Delayed Draw Notes
Debt Instrument [Line Items]
Revenue, net		$ 15,000,000
Total debt to trailing quarter net sales ratio		6.50

Long-Term Debt - Schedule of Long Term Debt (Details) - Senior Notes - Note Purchase Agreement $ in Thousands	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Face amount	$ 75,000
Front end fees	(999)
Debt issuance costs	(2,139)
Back end fees	1
Long-term Debt	$ 71,863

Employee Benefit Plans (Details) - USD ($)	12 Months Ended
Employee Benefit Plans (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Maximum annual contributions per employee	100.00%
Plan administrative expense	$ 230,000	$ 0
Foreign Plan
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost	$ 45,000	$ 24,000	$ 24,000
Defined Contribution Plan, Tranche One
Defined Contribution Plan Disclosure [Line Items]
Maximum annual contributions per employee	3.00%
Employer matching contribution	100.00%
Defined Contribution Plan, Tranche Two
Defined Contribution Plan Disclosure [Line Items]
Maximum annual contributions per employee	2.00%
Employer matching contribution	50.00%

Commitments and Contingencies (Leases) (Details) $ in Thousands	1 Months Ended	12 Months Ended			38 Months Ended
	Jan. 31, 2018 ft²	Dec. 31, 2017 USD ($) ft² lease	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	May 31, 2021 USD ($)
Subsequent Event [Line Items]
Number of operating leases \| lease		4
Rent expense \| $		$ 689	$ 407	$ 312
Area of real estate property \| ft²		20,050
Subsequent Event
Subsequent Event [Line Items]
Area of real estate property \| ft²	30,000
Renewal term	3 years
Subsequent Event \| Scenario, Forecast
Subsequent Event [Line Items]
Rent expense \| $					$ 2,750

Commitments and Contingencies (Future Minimum Lease Payments) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Future minimum annual payments, 2018	$ 187
Total future minimum lease payments as of December 31, 2017	$ 187

Commitments and Contingencies (Purchase Commitments) (Details) - USD ($)	Dec. 31, 2017	Nov. 30, 2017
Other Commitments [Line Items]
Purchase obligation	$ 0
Market Salesforce
Other Commitments [Line Items]
Contractual obligation		$ 16,354
Minimum \| Market Salesforce
Other Commitments [Line Items]
Early contract termination fees		100
Maximum \| Market Salesforce
Other Commitments [Line Items]
Early contract termination fees		$ 700

Stockholders' equity (deficit) - Common Stock (Details) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) vote $ / shares shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($)	Sep. 30, 2017 shares
Class of Stock [Line Items]
Shares authorized (in shares) \| shares		200,000,000	10,624,486
Net proceeds from IPO \| $		$ 138,000	$ 0	$ 0
Vote per share \| vote		1
Dividends declared (usd per share) \| $ / shares		$ 0
IPO
Class of Stock [Line Items]
Shares authorized (in shares) \| shares		13,067,149
Price per share (usd per share) \| $ / shares	$ 16.00
Net proceeds from IPO \| $	$ 125,471
Fees and commissions \| $	9,660
Stock issuance costs \| $	$ 2,869
IPO \| Common Stock
Class of Stock [Line Items]
Shares authorized (in shares) \| shares	200,000,000				10,624,486
Number of shares issued (in shares) \| shares	8,625,000

Stockholders' equity (deficit) (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Mar. 24, 2017	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2017
Temporary Equity [Line Items]
Common shares authorized (in shares)			200,000,000	10,624,486
Temporary equity, shares authorized (in shares)			8,932,851	6,875,514
Preferred stock, shares authorized (in shares)		5,000,000
Preferred stock, par value (in dollars per share)		$ 0.001
Preferred stock, shares issued (in shares)			0
Preferred stock, shares outstanding (in shares)			0
Redeemable Convertible Preferred Stock, Series D
Temporary Equity [Line Items]
Sale of Series D preferred stock, net of issuance costs (in shares)			1,117,578
Price per share (usd per share)			$ 32.85
Proceeds from the sale of Series D preferred stock			$ 36,712	$ 0	$ 0
Temporary equity, shares authorized (in shares)			1,369,863
Redeemable Convertible Preferred Stock, Series C2
Temporary Equity [Line Items]
Temporary equity, shares authorized (in shares)			687,474
Conversion at Consummation of IPO \| Common Stock
Temporary Equity [Line Items]
Shares issued, conversion of stock (in shares)		25,068,556
Conversion of Convertible notes into Series C2 Preferred Stock
Temporary Equity [Line Items]
Debt conversion, original debt amount			$ 19,527
Conversion of Convertible notes into Series C2 Preferred Stock \| Redeemable Convertible Preferred Stock, Series C2
Temporary Equity [Line Items]
Debt conversion shares issued (in shares)	687,474		687,474
Debt conversion, price per share (usd per share)	$ 28.40		$ 28.40
IPO
Temporary Equity [Line Items]
Price per share (usd per share)		$ 16.00
Common shares authorized (in shares)			13,067,149
IPO \| Common Stock
Temporary Equity [Line Items]
Sale of Series D preferred stock, net of issuance costs (in shares)		8,625,000
Common shares authorized (in shares)		200,000,000				10,624,486

Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercised (in shares)	41,283	18,049
Service Based Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Granted (in shares)	2,341,096
Fair value of common stock (in dollars per share)	$ 9.68
Intrinsic value of exercised options	$ 435	$ 20
Exercised (in shares)	26,047		0
Intrinsic value of options outstanding	$ 40,102
Intrinsic value of exercisable options	21,961
Unrecognized compensation cost	$ 22,198
Unrecognized compensation, estimated weighted-average amortization period	3 years 10 months 21 days
Performance Based Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Plan options contractual life	10 years
Granted (in shares)	0
Intrinsic value of exercised options	$ 505	$ 20
Exercised (in shares)	30,393	0
Intrinsic value of options outstanding	$ 19,713
Intrinsic value of exercisable options	$ 18,592
Unrecognized compensation, estimated weighted-average amortization period	2 years 8 months 5 days
Unrecognized cost related to unvested stock options	$ 563
Amended and Restated Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under plan (shares)	6,894,445
Number of shares reserved for future issuance under plan (shares)	546,131
Yearly increase in shares reserved for future issuance	4.00%
Plan options contractual life	10 years
Award vesting period	4 years

Stock-based Compensation - Service-based stock options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Service-based stock options activity
Exercised (in shares)	(41,283)	(18,049)
Service Based Stock Options
Service-based stock options activity
Shares outstanding, beginning (in shares)	1,894,083
Granted (in shares)	2,341,096
Exercised (in shares)	(26,047)		0
Expired (in shares)	(2,887)
Forfeited (in shares)	(96,036)
Shares outstanding, ending (in shares)	4,110,209	1,894,083
Exercisable at end of period (in shares)	1,327,843
Vested and expected to vest at end of period(in shares)	4,110,209
Service-based stock options weighted average exercise price
Beginning balance, Weighted average exercise price (in dollars per share)	$ 3.09
Granted, Weighted average exercise price (in dollars per share)	14.00
Exercised, Weighted average exercise price (in dollars per share)	2.34
Expired, Weighted average exercise price (in dollars per share)	5.68
Forfeited, Weighted average exercise price (in dollars per share)	9.29
Ending balance, Weighted average exercise price (in dollars per share)	9.16	$ 3.09
Options exercisable, Weighted average exercise price per share (in dollars per share)	2.36
Vested and expected to vest, Weighted average exercise price per share (in dollars per share)	$ 9.16
Service-based stock options, additional disclosures
Options outstanding, Weighted average remaining contractual life	7 years 10 months 21 days	6 years 8 months 1 day
Options exercisable, Weighted average remaining contractual life	4 years 6 months 11 days
Vested and expected to vest, Weighted average remaining contractual life	7 years 10 months 21 days

Stock-based Compensation - Performance-based stock options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Performance-based stock options activity
Exercised (in shares)	(41,283)	(18,049)
Performance Based Stock Options
Performance-based stock options activity
Shares outstanding, beginning (in shares)	2,171,760
Granted (in shares)	0
Exercised (in shares)	(30,393)	0
Forfeited (in shares)	0
Shares outstanding, ending (in shares)	2,141,367	2,171,760
Exercisable at end of period (in shares)	1,708,181
Vested and expected to vest at end of period(in shares)	2,141,367
Performance-based stock options weighted average exercise price
Beginning balance, Weighted average exercise price (in dollars per share)	$ 9.59
Granted, Weighted average exercise price (in dollars per share)	0.00
Exercised, Weighted average exercise price (in dollars per share)	2.44
Forfeited, Weighted average exercise price (in dollars per share)	0.00
Ending balance, Weighted average exercise price (in dollars per share)	9.69	$ 9.59
Options exercisable, Weighted average exercise price per share (in dollars per share)	8.02
Vested and expected to vest, Weighted average exercise price per share (in dollars per share)	$ 9.69
Performance-based stock options, additional disclosures
Options outstanding, Weighted average remaining contractual life	5 years 6 months 22 days	6 years 6 months 18 days
Options exercisable,Weighted average remaining contractual life	5 years 15 days
Vested and expected to vest, Weighted average remaining contractual life	5 years 6 months 22 days

Stock-based Compensation - Employee stock purchase plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 19, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 5,096	$ 599	$ 588
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under plan (shares)				144,395
Increase in number of shares issuable each year	1.00%
Stock-based compensation expense	$ 106

Stock-based Compensation - Stock-based compensation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 5,096	$ 599	$ 588
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	1,288	362	354
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,808	$ 237	$ 234

Stock-based Compensation - Black-Scholes pricing model options (Details)	12 Months Ended
	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual dividend yield	0.00%
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	1.27%
Expected term (in years)	8 months 19 days
Expected volatility	91.18%
Annual dividend yield	0.00%
2010 A & R Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	2.06%
Expected term (in years)	6 years 22 days
Expected volatility	78.67%
Annual dividend yield	0.00%

Income Taxes - Narrative (Details)	12 Months Ended
Income Taxes - Narrative (Details)	Dec. 31, 2017 USD ($)
Operating Loss Carryforwards [Line Items]
Income tax benefit (expense)	$ 0
Valuation allowance increase (decrease)	8,492,000
Unrecognized tax benefits, income tax penalties and interest accrued	0
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	96,616,000
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	30,327,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 13,702,000

Income Taxes - Schedule of Income before Income Tax, Domestic and Foreign (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Domestic operations	$ (30,463)	$ (4,967)
Foreign operations	(18,439)	27,580
Income (loss) before provision for income taxes	$ (48,902)	$ 22,613

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income tax expense at statutory rate	35.00%	35.00%
Permanent items	0.50%	0.00%
Foreign rate differential	(4.20%)	(12.20%)
State taxes, net of federal benefit	0.80%	(1.40%)
Tax rate changes	(15.40%)	0.00%
Change in valuation allowance	(16.70%)	(21.40%)
Effective income tax rate	0.00%	0.00%

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Accrued expenses and other	$ 972	$ 539
Fixed assets	55	0
Interest expense	783	677
Stock compensation	1,701	1,092
Research and development	2,485	2,183
Net operating losses	29,636	22,695
Total deferred tax assets	35,632	27,186
Deferred tax liabilities:
Fixed assets	0	(46)
Total deferred tax liabilities:	0	(46)
Less: Valuation allowance	(35,632)	(27,140)
Total net deferred tax assets (liabilities)	$ 0	$ 0

Related-party transactions (Details) $ in Thousands	12 Months Ended
Related-party transactions (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Investor \| Fees For IPO And Series D Convertible Stock
Related Party Transaction [Line Items]
Amount of transaction	$ 157

Quarterly Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 47,500	$ 0	$ 47,500	$ 85
Research and development	1,212	6,641	5,906	3,073	3,070	3,868	3,412	4,961	16,832	15,311	22,156
Selling, general and administrative	18,484	6,553	2,431	4,230	1,812	1,761	1,046	2,250	31,698	6,869	6,006
Total operating expenses	19,696	13,194	8,337	7,303	4,882	5,629	4,458	7,211	48,530	22,180	28,162
Income (loss) from operations	(19,696)	(13,194)	(8,337)	(7,303)	(4,882)	(5,629)	(4,458)	40,289	(48,530)	25,320	(28,077)
Net (loss) income	(19,551)	(13,068)	(8,208)	(8,075)	(5,588)	(6,106)	(5,265)	39,572	(48,902)	22,613	(28,314)
Net income (loss) attributable to common stockholders	$ (20,268)	$ (17,192)	$ (12,836)	$ (11,671)	$ (8,866)	$ (9,385)	$ (8,544)	$ 36,294	$ (61,967)	$ 9,499	$ (40,375)
Basic net income (loss) per common share (USD per share)	$ (0.64)	$ (4.23)	$ (3.16)	$ (2.87)	$ (2.18)	$ (2.32)	$ (2.10)	$ 1.52	$ (5.63)	$ 0.40	$ (9.97)
Diluted net income (loss) per common share (USD per share)	$ (0.64)	$ (4.23)	$ (3.16)	$ (2.87)	$ (2.18)	$ (2.32)	$ (2.10)	$ 1.25	$ (5.63)	$ 0.32	$ (9.97)

Related-party transactions	12 Months Ended
Related-party transactions	Dec. 31, 2017
Related Party Transactions [Abstract]
Related-party transactions	Related-party transactions Debt and equity transactions All of the Company's convertible debt (see Note 8) was issued to holders of the Company's convertible preferred stock. During the year-ended December 31, 2017, the Company reimbursed Avista Capital Holdings, LP and related parties $157 in expenses, primarily related to legal fees incurred in conjunction with our IPO in October 2017 and the issuance of Series D redeemable convertible preferred stock March 2017.

Stockholders' equity (deficit) - Warrants (Details)	Dec. 31, 2017 $ / shares shares
Equity [Abstract]
Number of warrants outstanding (in shares) \| shares	1,890,489
Common stock warrant exercise price (in dollars per share) \| $ / shares	$ 8.16

Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Deficit (Parenthetical)	12 Months Ended
	Dec. 31, 2017
Redeemable Convertible Preferred Stock, Series C, C1, C2, and D
Dividend rate	8.00%